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368Why setState(prev => ...) Exists
369The Closure Trap with Direct Updates
370Functional Update Syntax
371Guaranteeing Sequential Updates
372Functional Updates in Event Handlers
373Functional Updates in useEffect
374Functional Updates with Objects
375When Direct Updates Are Fine
376Performance: Functional Updates Are Not Slower
377Common Mistake: Mutating prevState
378When Multiple useState Calls Make Sense
379The Single Object Approach: Pros and Cons
380Updating Object State: The Spread Trap
381Independent Updates: The Key Decision Factor
382Related State That Changes Together
383Form State: When Objects Win
384Performance: Object vs Multiple Variables
385useReducer as the Middle Ground
386Migration Path: Refactoring Between Patterns
387What is Lazy Initialization?
388The Performance Problem with Direct Values
389Function Form: useState(() => value)
390Reading from localStorage Lazily
391Computing Derived Initial State
392When Lazy Init is Overkill
393Lazy Init vs useMemo: Different Tools
394The Stale Closure Problem in Async Callbacks
395Stale State in setTimeout and setInterval
396The Functional Update Solution
397Stale State in Event Listeners
398useRef for Mutable Current Values
399The useEffect Cleanup Race Condition
400Ignore Flags for Async Operations
401AbortController for Fetch Requests
402Stale Props in Async Callbacks
403The useEvent Hook Pattern (Upcoming)
404Debugging Stale State with Logging

368Why setState(prev => ...) Exists
369The Closure Trap with Direct Updates
370Functional Update Syntax
371Guaranteeing Sequential Updates
372Functional Updates in Event Handlers
373Functional Updates in useEffect
374Functional Updates with Objects
375When Direct Updates Are Fine
376Performance: Functional Updates Are Not Slower
377Common Mistake: Mutating prevState
378When Multiple useState Calls Make Sense
379The Single Object Approach: Pros and Cons
380Updating Object State: The Spread Trap
381Independent Updates: The Key Decision Factor
382Related State That Changes Together
383Form State: When Objects Win
384Performance: Object vs Multiple Variables
385useReducer as the Middle Ground
386Migration Path: Refactoring Between Patterns
387What is Lazy Initialization?
388The Performance Problem with Direct Values
389Function Form: useState(() => value)
390Reading from localStorage Lazily
391Computing Derived Initial State
392When Lazy Init is Overkill
393Lazy Init vs useMemo: Different Tools
394The Stale Closure Problem in Async Callbacks
395Stale State in setTimeout and setInterval
396The Functional Update Solution
397Stale State in Event Listeners
398useRef for Mutable Current Values
399The useEffect Cleanup Race Condition
400Ignore Flags for Async Operations
401AbortController for Fetch Requests
402Stale Props in Async Callbacks
403The useEvent Hook Pattern (Upcoming)
404Debugging Stale State with Logging

Lesson 374 of 2,396·11. useState Patterns and PitfallsPro lesson

Functional Updates with Objects

Pattern: setState(prev => ({ ...prev, field: newValue })) to safely update object state without losing other fields.

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